Motorists do not believe the government's claims that road taxes help cut carbon dioxide emissions and boost public transport investment, according to an MPs' report released today which recommends a voluntary "pay as you drive" scheme.

The report, by the Commons transport committee, urges ministers to revive the idea of giving motorists the option of being taxed per mile driven – one of the most controversial government proposals of recent years. The recommendation comes with a warning that says the motoring public has become "mistrustful" of taxes on road users.

The committee's chair, Louise Ellman, Labour MP for Liverpool Riverside, said recent increases in vehicle excise duty had been handled so badly the image of environmental taxes had been tarnished.

The report says: "The government has been inconsistent in the way that it has justified motoring taxes. Fuel duty has been presented, at different times, as a tool to reduce carbon emissions, a source of general revenue, and a means to fund transport investment. We are concerned that motorists are mistrustful of the government regarding taxes."

The idea is that "pay as you drive" schemes could be used as a substitute for excise duty or fuel duty payments.

Road pricing remains a politically toxic subject for the government after nearly 2 million people signed an online Downing Street petition condemning the concept two years ago.

However, the reintroduction of road pricing into the tax debate was welcomed by one leading motorists' thinktank. The RAC Foundation said a charging scheme "might become unavoidable" but ministers had to restore belief in the purpose of road taxes first.

Taxes on drivers raise about £45bn a year for the Treasury, say motorists' groups.

Stephen Glaister, director of the RAC Foundation, said motorists would not back a revised road tax system with the "apparent sole intention of shoring up the nation's ailing finances". He added: "For any radical policy to be successful, public trust in the politicians introducing it is essential. That trust is lacking."

According to an AA poll, 86% of UK drivers do not believe the government would deliver a fair road-pricing programme. Edmund King, the AA's president, said the introduction of even a small scheme would be "some way off" because of the online petition revolt and the recent rejection of a congestion charge by voters in Manchester. "Voluntary or not, it would be very difficult to introduce at the moment," he said.

A Treasury spokesperson said: "Government has always been very clear that transport taxes are primarily revenue-raising – but that they also send strong environmental signals, encouraging greater fuel efficiency, and the purchase of lower-emitting cars."